x1:3,2c3-2c1+l(l+1l1=0 (+1)-2 3.2 [(+1)-k(k+1 k+2 (k+2)(+1) 2+l-2.3 2(-2)(+1)(1+ (-1)1 3 1 1 x : 3× 2c - 2c + l(l c + = 1) 0 3 1 ( 1)-2 - 3 2 l l c c + \ = × [ ] ( ) 2 ( 1) - ( 1) : - 3 ( 2) ( 1) k k k l l k k x c c k l + + + = + × + 2 4 2 - 2 3 - 4 3 l l c c + × \ = × ( ) 2 ( ) ( )( ) 0 - 2 1 3 -1 4! l l l l c + + =